1. Field of the Invention
The invention relates to an improved ski equipped with a device for modifying the stiffness and/or shock absorption, as a function of the deformation of the ski during use.
2. Discussion of Background and Material Information
The majority of existing shock absorbers or stiffening systems for skis are provided in such a way that the response, in terms of shock absorption and stiffness, is proportional to the bending force exerted on the ski (what the specialist calls "the deformation" of the ski). An example of such a system is disclosed in U.S. Pat. No. 5,251,923, wherein it is illustrated in FIGS. 1-3. The device comprises a rod whose one end is rigidly fixed to a given location on the ski and the other end is translationally free beneath a predetermined bending or flexion f1 of the ski.
In this first configuration (FIG. 1), the ski is a beam having its own rigidity R that increases in a substantially linear fashion as a function of the flexion of the ski. Beyond a certain flexion value f1, the free end cooperates with an abutment system that resists the displacement of the rod whose rigidity is added to that of the ski (FIG. 3). In other words, beyond a flexion value limit f1, the ski becomes much more stiff and directive.
But, the applicant has discovered that a ski equipped with such a device leads to a very controllable and thus very stable device, but on the other hand, one that is difficult to manoeuver. Proceeding from this observation, the applicant has researched solutions that could bring about a better pivoting ability compromise in order to obtain an efficient ski in all high-speed steering situations. In particular, it has been shown that in a horizontal position or during engagement of large radius curves, it is necessary to have a ski that perfectly follows the trajectory with great precision and good stability. It is thus necessary to increase or at least maintain the stiffness and shock absorbing qualities of previous devices.
On the other hand, it has also been discovered that it is necessary to facilitate the deformation of the ski to facilitate reentry into a tight curve in order to have a ski that can be turned just as easily.
Among the devices of the prior art, a stiffening effect proportional to the bending exerted on the ski is found in French Patent Publication No. 2 689 411. In this case, the ski comprises two stiffening elements attached on the base body which cooperate among themselves as to a given bending value so as to increase the overall stiffness of the ski.
In French Patent Publication Nos. 2 675 392, 2 678 517, and 2 694 205 the devices are shock absorbers that also operate according to the principle that when the deformation of the ski increases, the response in terms of shock absorption increases proportionally.
In the state of the art, it is also known to the contrary that in order to facilitate pivoting about the center of gravity of the skier, it is preferable to relieve the ends of the ski from the pressure exerted by the weight of the skier. Such a teaching is described in the prior art documents such as German Patent Publication No. 79 12 699 and French Patent Publication No. 810 762. The invention described in these two documents relates to a ski equipped with an inverted camber base on which a normal camber stiffener is attached. Thus, when the ski is relieved of the weight of the skier, the ends rise under the effect of the base camber and when the skier rests on the ski, the stiffener cancels the base camber and presses the ends against the snow. The disadvantage of these devices resides in the fact that at the moment of turn initiation, any relief of the ends of the ski cannot realistically intervene by reason of the fact that the skier exerts a substantial effort on the ski to avoid any skidding. It is fitting to note that such devices are inefficient and do not respond in terms of a solution to the realities of the operation of a ski on snow.
Finally, in the prior art, applicants are aware of French Patent Publication No. 2 686 798 whose object is an interactive device aiming, conversely, to increase the pressure on the "active" ends of the ski by direct support of the boot on the device. What must be understood by "active" ends are the portions in contact with the snow as opposed to the raised ends that are the shovel and tail.
In the case of the present invention, the boot does not exert any direct effect on the device to modify the distribution of pressure on the snow.